Method and apparatus for forming fiber reinforced plastic preforms from a wet slurry

Abstract

A method and apparatus for making fiber reinforced plastic preforms via a wet slurry process. A screen with the desired preform configuration is placed in the bottom of a tank. The tank is then filled with water and chopped fibers to create a slurry. The screen is raised up through the slurry causing fibers to be deposited on the screen in the shape of the preform. The preform is then removed from the screen, placed in a mold and injected with resin to form the desired structure.

What is claimed is: 
     
       1. A method of forming a structure from a fiber reinforced plastic preform which comprises: (a) placing a screen shaped to a desired preform configuration near the bottom of a tank filled with a liquid, said screen having a preselected geometry of openings with hole patterns of non-uniform size, shape and orientation;   (b) adding reinforcing fibers to the liquid to create a slurry;   (c) raising the screen to the top of the tank causing the fibers to be deposited on the screen thereby generating a preform, said preselected geometry or openings in the screen causing the fibers to be deposited in preselected orientations related to the orientation of the holes in the screen;   (d) removing the preform from the screen;   (e) placing the preform in a mold;   (f) injecting resin into the mold to impregnate the fibers in the preform to thereby form the desired structure; and   (g) removing the structure from the mold.   
     
     
       2. The method of claim 1 wherein the preselected geometry of openings in the screen comprises a first region of elongated slots lying in a given direction and at least one more region of elongated slots lying in a different direction relative to the given direction of the first region. 
     
     
       3. The method of claim 1 which further comprises the step of: removing the preform from the screen by a vacuum pickup device. 
     
     
       4. The method of claim 1 which further comprises the step of: using a bubbler to mix the liquid and fibers together to create a substantially even dispersion of fibers in the slurry. 
     
     
       5. An apparatus for forming fiber reinforced plastic preforms comprising: (a) a tank having a top portion and a bottom portion, the tank containing a slurry of liquid and a mass of fibers;   (b) a contoured screen having a predetermined configuration, said contoured screen containing openings and being disposed within said tank;   (c) frame means for supporting the screen;   (d) means for raising the contoured screen vertically toward the top portion of the tank at a sufficient rate to create a downward force which causes the slurry of liquid to pass through the openings in the screen whereby the fibers are deposited on the screen to form a preform having substantially the same configuration as the contoured screen and having a sufficient mass of fibers to form a fiber reinforced plastic part when injected with resin; and   (e) vacuum pickup means for removing the preform from the screen, the pickup means having an engagement surface complimentary to the contoured screen.   
     
     
       6. The apparatus of claim 5 further comprising: bubbler means located adjacent to the screen for mixing the liquid and fibers together to create a substantially even dispersion of the fibers in the slurry, said bubbler means including a perforated tubing; an air source; and an air passageway from the source to the perforated tubing, with part of said passageway including a hollow space in a piston for raising the screen. 
     
     
       7. The apparatus for forming fiber reinforced plastic preforms comprising: (a) a tank containing a slurry of liquid and fibers;   (b) a screen having a preselected geometry of openings with hole patterns of non-uniform size, shape and orientation;   (c) frame means for supporting the screen; and   (d) means for causing the slurry to flow through the screen and deposit the fibers on the screen, said preselected geometry of openings in the screen causing the fibers to be deposited in preselected orientations related to the orientation of the holes in the screen.   
     
     
       8. The apparatus of claim 7 wherein the preselected geometry of openings in the screen comprises a first region of elongated slots lying in a given direction and at least one more region of elongated slots lying in a different direction relative to the given direction of the first region. 
     
     
       9. An apparatus for forming fiber reinforced plastic preforms comprising: (a) a tank containing a slurry of liquid and fibers;   (b) a screen;   (c) frame means for supporting the screen;   (d) means for raising the screen to cause the fibers to be deposited on the screen; and   (e) bubbler means located adjacent to and carried with the screen for mixing the liquid and fibers together to create a substantially even dispersion of the fibers in the slurry.   
     
     
       10. The apparatus of claim 9 where said bubbler means comprises: a perforated tubing carried by the frame means: (a) an air source; and   (b) an air passageway from the air source to the tubing, with part of said passageway being through the means for raising the screen.